Method and system for controlling a robot

ABSTRACT

A system and method are described that use impulse radio technology to enhance the capabilities of a robot. In one embodiment, a system, a robot and a method are provided that use the communication capabilities of impulse radio technology to help a control station better control the actions of the robot. In another embodiment, a system, a robot and a method are provided that use the communication, position and/or radar capabilities of impulse radio technology to help a control station better control the actions of a robot in order to, for example, monitor and control the environment within a building.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. patentapplication Ser. No. 10/826,440, filed Apr. 17, 2004, now pending, whichis a continuation application of U.S. Pat. No. 6,763,282 B2.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to robots and, in particular,to a system and method capable of using impulse radio technology toenhance the capabilities of a robot.

2. Description of Related Art

In the robotics field, one of the most significant design challengesinvolves the development of new ways to improve the way a controlstation can interact with and control the actions of a robot. To datemany control stations have a standard radio transceiver, which transmitsand receives radio signals to and from another standard radiotransceiver attached to the robot in order to interact with and controlthe actions of that robot. Unfortunately, problems have arisen in thepast with the use of standard radio equipment because there are oftenproblematical “dead zones” within a building that may interfere with thecommunications between the control station and a moving robot. Deadzones are caused by the closed structure of the building, which can makeit difficult for a moving robot using a standard radio transceiver tomaintain contact with a control station using a standard radiotransceiver. For instance, the standard radio signals sent from thestandard radio transceiver attached to the control station may not beable to penetrate a certain wall or floor within the building and assuch may not reach the standard radio transceiver attached to the movingrobot.

The closed structure of the building may also cause “multipathinterference” which can interfere with standard radio transmissionsbetween the control station and the robot. Multipath interference is anerror caused by the interference of a standard radio signal that hasreached a standard radio receiver by two or more paths. For instance,the standard radio receiver attached to the robot may not be able todemodulate a received radio signal because the originally transmittedradio signal effectively cancels itself out by bouncing of walls andfloors of the building before reaching the robot. Accordingly, there hasbeen a need to provide a system, robot and method that can overcome thetraditional shortcomings associated with communications between thecontrol station and robot. This need and other needs are addressed bythe system, robot and method of the present invention.

BRIEF DESCRIPTION OF THE INVENTION

The present invention includes a system and method capable of usingimpulse radio technology to enhance the capabilities of a robot. In oneembodiment of the present invention, a system, a robot and a method areprovided that use the communication capabilities of impulse radiotechnology to help a control station better control the actions of therobot. In another embodiment of the present invention, a system, a robotand a method are provided that use the communication, position and/orradar capabilities of impulse radio technology to help a control stationbetter control the actions of a robot in order to, for example, monitorand control the environment within a building.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be had byreference to the following detailed description when taken inconjunction with the accompanying drawings wherein:

FIG. 1A illustrates a representative Gaussian Monocycle waveform in thetime domain;

FIG. 1B illustrates the frequency domain amplitude of the GaussianMonocycle of FIG. 1A;

FIG. 1C represents the second derivative of the Gaussian Monocycle ofFIG. 1A;

FIG. 1D represents the third derivative of the Gaussian Monocycle ofFIG. 1A;

FIG. 1E represents the Correlator Output vs. the Relative Delay in areal data pulse;

FIG. 1F graphically depicts the frequency plot of the Gaussian family ofthe Gaussian Pulse and the first, second, and third derivative.

FIG. 2A illustrates a pulse train comprising pulses as in FIG. 1A;

FIG. 2B illustrates the frequency domain amplitude of the waveform ofFIG. 2A;

FIG. 2C illustrates the pulse train spectrum;

FIG. 2D is a plot of the Frequency vs. Energy Plot and points out thecoded signal energy spikes;

FIG. 3 illustrates the cross-correlation of two codes graphically asCoincidences vs. Time Offset;

FIG. 4A-4E graphically illustrate five modulation techniques to include:Early-Late Modulation; One of Many Modulation; Flip Modulation; QuadFlip Modulation; and Vector Modulation;

FIG. 5A illustrates representative signals of an interfering signal, acoded received pulse train and a coded reference pulse train;

FIG. 5B depicts a typical geometrical configuration giving rise tomultipath received signals;

FIG. 5C illustrates exemplary multipath signals in the time domain;

FIGS. 5D-5F illustrate a signal plot of various multipath environments.

FIGS. 5G illustrates the Rayleigh fading curve associated withnon-impulse radio transmissions in a multipath environment.

FIG. 5H illustrates a plurality of multipaths with a plurality ofreflectors from a transmitter to a receiver.

FIG. 5I graphically represents signal strength as volts vs. time in adirect path and multipath environment.

FIG. 6 illustrates a representative impulse radio transmitter functionaldiagram;

FIG. 7 illustrates a representative impulse radio receiver functionaldiagram;

FIG. 8A illustrates a representative received pulse signal at the inputto the correlator;

FIG. 8B illustrates a sequence of representative impulse signals in thecorrelation process;

FIG. 8C illustrates the output of the correlator for each of the timeoffsets of FIG. 8B.

FIG. 9 is a diagram illustrating the basic components of a system inaccordance with the present invention.

FIG. 10 is a diagram illustrating in greater detail the components of arobot and control station of the system shown in FIG. 9.

FIG. 11 is a diagram illustrating the robot and control station of FIG.10 used in a manner to monitor and control, if needed, the environmentwithin a building.

FIG. 12 is a diagram illustrating in greater detail the robot andcontrol station of FIG. 10 used in a manner to monitor and trackphysical assets within the building.

FIG. 13 is a flowchart illustrating the basic steps of a preferredmethod for controlling the actions of a robot in accordance with thepresent invention.

FIG. 14 is a block diagram of an impulse radio positioning networkutilizing a synchronized transceiver tracking architecture that can beused in the present invention.

FIG. 15 is a block diagram of an impulse radio positioning networkutilizing an unsynchronized transceiver tracking architecture that canbe used in the present invention.

FIG. 16 is a block diagram of an impulse radio positioning networkutilizing a synchronized transmitter tracking architecture that can beused in the present invention.

FIG. 17 is a block diagram of an impulse radio positioning networkutilizing an unsynchronized transmitter tracking architecture that canbe used in the present invention.

FIG. 18 is a block diagram of an impulse radio positioning networkutilizing a synchronized receiver tracking architecture that can be usedin the present invention.

FIG. 19 is a block diagram of an impulse radio positioning networkutilizing an unsynchronized receiver tracking architecture that can beused in the present invention.

FIG. 20 is a diagram of an impulse radio positioning network utilizing amixed mode reference radio tracking architecture that can be used in thepresent invention.

FIG. 21 is a diagram of an impulse radio positioning network utilizing amixed mode mobile apparatus tracking architecture that can be used inthe present invention.

FIG. 22 is a diagram of a steerable null antennae architecture capableof being used in an impulse radio positioning network in accordance thepresent invention.

FIG. 23 is a diagram of a specialized difference antennae architecturecapable of being used in an impulse radio positioning network inaccordance the present invention.

FIG. 24 is a diagram of a specialized directional antennae architecturecapable of being used in an impulse radio positioning network inaccordance with the present invention.

FIG. 25 is a diagram of an amplitude sensing architecture capable ofbeing used in an impulse radio positioning network in accordance withthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes a system and method capable of usingimpulse radio technology to enhance the capabilities of a robot. The useof impulse radio technology to enhance the capabilities of a robot is asignificant improvement over the state-of-art. This significantimprovement over the state-of-art is attributable, in part, to the useof an emerging, revolutionary ultra wideband technology (UWB) calledimpulse radio communication technology (also known as impulse radio).

Impulse radio, which is not a continuous wave carrier-based system, hasbeen described in a series of patents, including U.S. Pat. No. 4,641,317(issued Feb. 3, 1987), U.S. Pat. No. 4,813,057 (issued Mar. 14, 1989),U.S. Pat. No. 4,979,186 (issued Dec. 18, 1990) and U.S. Pat. No.5,363,108 (issued Nov. 8, 1994) to Larry W. Fullerton. A secondgeneration of impulse radio patents includes U.S. Pat. No. 5,677,927(issued Oct. 14, 1997), U.S. Pat. No. 5,687,169 (issued Nov. 11, 1997),U.S. Pat. No. 5,764,696 (issued Jun. 9, 1998), and U.S. Pat. No.5,832,035 (issued Nov. 3, 1998) to Fullerton et al.

Uses of impulse radio systems are described in U.S. Pat. No. 6,177,903entitled, “System and Method for Intrusion Detection using a Time DomainRadar Array” and U.S. Pat. No. 6,218,979 entitled, “Wide Area TimeDomain Radar Array” both of which are assigned to the assignee of thepresent invention. These patents are incorporated herein by reference.

This section provides an overview of impulse radio technology andrelevant aspects of communications theory. It is provided to assist thereader with understanding the present invention and should not be usedto limit the scope of the present invention. It should be understoodthat the terminology ‘impulse radio’ is used primarily for historicalconvenience and that the terminology can be generally interchanged withthe terminology ‘impulse communications system, ultra-wideband system,or ultra-wideband communication systems’. Furthermore, it should beunderstood that the described impulse radio technology is generallyapplicable to various other impulse system applications including butnot limited to impulse radar systems and impulse positioning systems.Accordingly, the terminology ‘impulse radio’ can be generallyinterchanged with the terminology ‘impulse transmission system andimpulse reception system.’

Impulse radio refers to a radio system based on short, low duty-cyclepulses. An ideal impulse radio waveform is a short Gaussian monocycle.As the name suggests, this waveform attempts to approach one cycle ofradio frequency (RF) energy at a desired center frequency. Due toimplementation and other spectral limitations, this waveform may bealtered significantly in practice for a given application. Manywaveforms having very broad, or wide, spectral bandwidth approximate aGaussian shape to a useful degree.

Impulse radio can use many types of modulation, including amplitudemodulation, phase modulation, frequency modulation, time-shiftmodulation (also referred to as pulse-position modulation orpulse-interval modulation) and M-ary versions of these. In thisdocument, the time-shift modulation method is often used as anillustrative example. However, someone skilled in the art will recognizethat alternative modulation approaches may, in some instances, be usedinstead of or in combination with the time-shift modulation approach.

In impulse radio communications, inter-pulse spacing may be heldconstant or may be varied on a pulse-by-pulse basis by information, acode, or both. Generally, conventional spread spectrum systems employcodes to spread the normally narrow band information signal over arelatively wide band of frequencies. A conventional spread spectrumreceiver correlates these signals to retrieve the original informationsignal. In impulse radio communications, codes are not typically usedfor energy spreading because the monocycle pulses themselves have aninherently wide bandwidth. Codes are more commonly used forchannelization, energy smoothing in the frequency domain, resistance tointerference, and reducing the interference potential to nearbyreceivers. Such codes are commonly referred to as time-hopping codes orpseudo-noise (PN) codes since their use typically causes inter-pulsespacing to have a seemingly random nature. PN codes may be generated bytechniques other than pseudorandom code generation. Additionally, pulsetrains having constant, or uniform, pulse spacing are commonly referredto as uncoded pulse trains. A pulse train with uniform pulse spacing,however, may be described by a code that specifies non-temporal, i.e.,non-time related, pulse characteristics.

In impulse radio communications utilizing time-shift modulation,information comprising one or more bits of data typically time-positionmodulates a sequence of pulses. This yields a modulated, coded timingsignal that comprises a train of pulses from which a typical impulseradio receiver employing the same code may demodulate and, if necessary,coherently integrate pulses to recover the transmitted information.

The impulse radio receiver is typically a direct conversion receiverwith a cross correlator front-end that coherently converts anelectromagnetic pulse train of monocycle pulses to a baseband signal ina single stage. The baseband signal is the basic information signal forthe impulse radio communications system. A subcarrier may also beincluded with the baseband signal to reduce the effects of amplifierdrift and low frequency noise. Typically, the subcarrier alternatelyreverses modulation according to a known pattern at a rate faster thanthe data rate. This same pattern is used to reverse the process andrestore the original data pattern just before detection. This methodpermits alternating current (AC) coupling of stages, or equivalentsignal processing, to eliminate direct current (DC) drift and errorsfrom the detection process. This method is described in more detail inU.S. Pat. No. 5,677,927 to Fullerton et al.

Waveforms

Impulse transmission systems are based on short, low duty-cycle pulses.Different pulse waveforms, or pulse types, may be employed toaccommodate requirements of various applications. Typical pulse typesinclude a Gaussian pulse, pulse doublet (also referred to as a Gaussianmonocycle), pulse triplet, and pulse quadlet as depicted in FIGS. 1Athrough 1D, respectively. An actual received waveform that closelyresembles the theoretical pulse quadlet is shown in FIG. 1E. A pulsetype may also be a wavelet set produced by combining two or more pulsewaveforms (e.g., a doublet/triplet wavelet set). These different pulsetypes may be produced by methods described in the patent documentsreferenced above or by other methods, as persons skilled in the artwould understand.

For analysis purposes, it is convenient to model pulse waveforms in anideal manner. For example, the transmitted waveform produced bysupplying a step function into an ultra-wideband antenna may be modeledas a Gaussian monocycle. A Gaussian monocycle (normalized to a peakvalue of 1) may be described by:${f_{mono}(t)} = {\sqrt{e}\left( \frac{t}{\sigma} \right){\mathbb{e}}^{\frac{- t^{2}}{2\sigma^{2}}}}$where σ is a time scaling parameter, t is time, and e is the naturallogarithm base.

The power special density of the Gaussian monocycle is shown in FIG. 1F,along with spectrums for the Gaussian pulse, triplet, and quadlet. Thecorresponding equation for the Gaussian monocycle is:F _(mono)(f)=(2π)^(3/2) σfe ^(−2(πσf))

The center frequency (f_(c)), or frequency of peak spectral density, ofthe Gaussian monocycle is: $f_{c} = \frac{1}{2{\pi\sigma}}$

It should be noted that the output of an ultra-wideband antenna isessentially equal to the derivative of its input. Accordingly, since thepulse doublet, pulse triplet, and pulse quadlet are the first, second,and third derivatives of the Gaussian pulse, in an ideal model, anantenna receiving a Gaussian pulse will transmit a Gaussian monocycleand an antenna receiving a Gaussian monocycle will provide a pulsetriplet.

Pulse Trains

Impulse transmission systems may communicate one or more data bits witha single pulse; however, typically each data bit is communicated using asequence of pulses, known as a pulse train. As described in detail inthe following example system, the impulse radio transmitter produces andoutputs a train of pulses for each bit of information. FIGS. 2A and 2Bare illustrations of the output of a typical 10 megapulses per second(Mpps) system with uncoded, unmodulated pulses, each having a width of0.5 nanoseconds (ns). FIG. 2A shows a time domain representation of thepulse train output. FIG. 2B illustrates that the result of the pulsetrain in the frequency domain is to produce a spectrum comprising a setof comb lines spaced at the frequency of the 10 Mpps pulse repetitionrate. When the full spectrum is shown, as in FIG. 2C, the envelope ofthe comb line spectrum corresponds to the curve of the single Gaussianmonocycle spectrum in FIG. 1F. For this simple uncoded case, the powerof the pulse train is spread among roughly two hundred comb lines. Eachcomb line thus has a small fraction of the total power and presents muchless of an interference problem to a receiver sharing the band. It canalso be observed from FIG. 2A that impulse transmission systemstypically have very low average duty cycles, resulting in average powerlower than peak power. The duty cycle of the signal in FIG. 2A is 0.5%,based on a 0.5 ns pulse duration in a 100 ns interval.

The signal of an uncoded, unmodulated pulse train may be expressed:${s(t)} = {\left( {- 1} \right)^{f}a{\sum\limits_{j}{\omega\left( {{{ct} - {jT}_{f}},b} \right)}}}$where j is the index of a pulse within a pulse train, (−1)^(f) ispolarity (+/−), a is pulse amplitude, b is pulse type, c is pulse width,ω(t,b) is the normalized pulse waveform, and T_(f) is pulse repetitiontime.

The energy spectrum of a pulse train signal over a frequency bandwidthof interest may be determined by summing the phasors of the pulses ateach frequency, using the following equation:${A(\omega)} = {{\sum\limits_{i = 1}^{n}\frac{e^{j\quad\Delta\quad t}}{n}}}$where A(ω) is the amplitude of the spectral response at a givenfrequency . . . ω. is the frequency being analyzed (2πf), Δt is therelative time delay of each pulse from the start of time period, and nis the total number of pulses in the pulse train.

A pulse train can also be characterized by its autocorrelation andcross-correlation properties. Autocorrelation properties pertain to thenumber of pulse coincidences (i.e., simultaneous arrival of pulses) thatoccur when a pulse train is correlated against an instance of itselfthat is offset in time. Of primary importance is the ratio of the numberof pulses in the pulse train to the maximum number of coincidences thatoccur for any time offset across the period of the pulse train. Thisratio is commonly referred to as the main-lobe-to-side-lobe ratio, wherethe greater the ratio, the easier it is to acquire and track a signal.

Cross-correlation properties involve the potential for pulses from twodifferent signals simultaneously arriving, or coinciding, at a receiver.Of primary importance are the maximum and average numbers of pulsecoincidences that may occur between two pulse trains. As the number ofcoincidences increases, the propensity for data errors increases.Accordingly, pulse train cross-correlation properties are used indetermining channelization capabilities of impulse transmission systems(i.e., the ability to simultaneously operate within close proximity).

Coding

Specialized coding techniques can be employed to specify temporal and/ornon-temporal pulse characteristics to produce a pulse train havingcertain spectral and/or correlation properties. For example, byemploying a PN code to vary inter-pulse spacing, the energy in the comblines presented in FIG. 2B can be distributed to other frequencies asdepicted in FIG. 2D, thereby decreasing the peak spectral density withina bandwidth of interest. Note that the spectrum retains certainproperties that depend on the specific (temporal) PN code used. Spectralproperties can be similarly affected by using non-temporal coding (e.g.,inverting certain pulses).

Coding provides a method of establishing independent communicationchannels. Specifically, families of codes can be designed such that thenumber of pulse coincidences between pulse trains produced by any twocodes will be minimal. For example, FIG. 3 depicts cross-correlationproperties of two codes that have no more than four coincidences for anytime offset. Generally, keeping the number of pulse collisions minimalrepresents a substantial attenuation of the unwanted signal.

Coding can also be used to facilitate signal acquisition. For example,coding techniques can be used to produce pulse trains with a desirablemain-lobe-to-side-lobe ratio. In addition, coding can be used to reduceacquisition algorithm search space.

Coding methods for specifying temporal and non-temporal pulsecharacteristics are described in commonly owned, co-pending applicationstitled “A Method and Apparatus for Positioning Pulses in Time,”application Ser. No. 09/592,249, and “A Method for SpecifyingNon-Temporal Pulse Characteristics,” application Ser. No. 09/592,250,both filed Jun. 12, 2000, and both of which are incorporated herein byreference.

Typically, a code consists of a number of code elements having integeror floating-point values. A code element value may specify a singlepulse characteristic or may be subdivided into multiple components, eachspecifying a different pulse characteristic. Code element or codecomponent values typically map to a pulse characteristic value layoutthat may be fixed or non-fixed and may involve value ranges, discretevalues, or a combination of value ranges and discrete values. A valuerange layout specifies a range of values that is divided into componentsthat are each subdivided into subcomponents, which can be furthersubdivided, as desired. In contrast, a discrete value layout involvesuniformly or non-uniformly distributed discrete values. A non-fixedlayout (also referred to as a delta layout) involves delta valuesrelative to some reference value. Fixed and non-fixed layouts, andapproaches for mapping code element/component values, are described inco-owned, co-pending applications, titled “Method for Specifying PulseCharacteristics using Codes,” application Ser. No. 09/592,290 and “AMethod and Apparatus for Mapping Pulses to a Non-Fixed Layout,”application Ser. No. 09/591,691, both filed on Jun. 12, 2000, both ofwhich are incorporated herein by reference.

A fixed or non-fixed characteristic value layout may include anon-allowable region within which a pulse characteristic value isdisallowed. A method for specifying non-allowable regions is describedin co-owned U.S. Pat. No. 6,636,567 which is entitled “A Method forSpecifying Non-Allowable Pulse Characteristics,” and is incorporatedherein by reference. A related method that conditionally positionspulses depending on whether code elements map to non-allowable regionsis described in co-owned, co-pending application, titled “A Method andApparatus for Positioning Pulses Using a Layout having Non-AllowableRegions,” application Ser. No. 09/592,248 filed Jun. 12, 2000, andincorporated herein by reference.

The signal of a coded pulse train can be generally expressed by:${s_{tr}^{(k)}(t)} = {\sum\limits_{j}{\left( {- 1} \right)^{f_{j}^{(k)}}a_{j}^{(k)}{\omega\left( {{{c_{j}^{(k)}t} - T_{j}^{(k)}},b_{j}^{(k)}} \right)}}}$where k is the index of a transmitter, j is the index of a pulse withinits pulse train, (−1)f_(j) ^((k)), a_(j) ^((k)), b_(j) ^((k)), c_(j)^((k)), and ω(t,b_(j) ^((k))) are the coded polarity, pulse amplitude,pulse type, pulse width, and normalized pulse waveform of the jth pulseof the kth transmitter, and T_(j) ^((k)) is the coded time shift of thejth pulse of the kth transmitter. Note: When a given non-temporalcharacteristic does not vary (i.e., remains constant for all pulses), itbecomes a constant in front of the summation sign.

Various numerical code generation methods can be employed to producecodes having certain correlation and spectral properties. Such codestypically fall into one of two categories: designed codes andpseudorandom codes. A designed code may be generated using a quadraticcongruential, hyperbolic congruential, linear congruential, Costasarray, or other such numerical code generation technique designed togenerate codes having certain correlation properties. A pseudorandomcode may be generated using a computer's random number generator, binaryshift-register(s) mapped to binary words, a chaotic code generationscheme, or the like. Such ‘random-like’ codes are attractive for certainapplications since they tend to spread spectral energy over multiplefrequencies while having ‘good enough’ correlation properties, whereasdesigned codes may have superior correlation properties but possess lesssuitable spectral properties. Detailed descriptions of numerical codegeneration techniques are included in a co-owned, co-pending patentapplication titled “A Method and Apparatus for Positioning Pulses inTime,” application Ser. No. 09/592,248, filed Jun. 12, 2000, andincorporated herein by reference.

It may be necessary to apply predefined criteria to determine whether agenerated code, code family, or a subset of a code is acceptable for usewith a given UWB application. Criteria may include correlationproperties, spectral properties, code length, non-allowable regions,number of code family members, or other pulse characteristics. A methodfor applying predefined criteria to codes is described in co-owned U.S.Pat. No. 6,636,566 which is entitled “A Method and Apparatus forSpecifying Pulse Characteristics using a Code that Satisfies PredefinedCriteria,” and is incorporated herein by reference.

In some applications, it may be desirable to employ a combination ofcodes. Codes may be combined sequentially, nested, or sequentiallynested, and code combinations may be repeated. Sequential codecombinations typically involve switching from one code to the next afterthe occurrence of some event and may also be used to support multicastcommunications. Nested code combinations may be employed to producepulse trains having desirable correlation and spectral properties. Forexample, a designed code may be used to specify value range componentswithin a layout and a nested pseudorandom code may be used to randomlyposition pulses within the value range components. With this approach,correlation properties of the designed code are maintained since thepulse positions specified by the nested code reside within the valuerange components specified by the designed code, while the randompositioning of the pulses within the components results in particularspectral properties. A method for applying code combinations isdescribed in co-owned U.S. Pat. No. 6,671,310 which is entitled “AMethod and Apparatus for Applying Codes Having Pre-Defined Properties,”and is incorporated herein by reference.

Modulation

Various aspects of a pulse waveform may be modulated to conveyinformation and to further minimize structure in the resulting spectrum.Amplitude modulation, phase modulation, frequency modulation, time-shiftmodulation and M-ary versions of these were proposed in U.S. Pat. No.5,677,927 to Fullerton et al., previously incorporated by reference.Time-shift modulation can be described as shifting the position of apulse either forward or backward in time relative to a nominal coded (oruncoded) time position in response to an information signal. Thus, eachpulse in a train of pulses is typically delayed a different amount fromits respective time base clock position by an individual code delayamount plus a modulation time shift. This modulation time shift isnormally very small relative to the code shift. In a 10 Mpps system witha center frequency of 2 GHz, for example, the code may command pulseposition variations over a range of 100 ns, whereas, the informationmodulation may shift the pulse position by 150 ps. This two-state‘early-late’ form of time shift modulation is depicted in FIG. 4A.

A pulse train with conventional ‘early-late’ time-shift modulation canbe expressed:${s_{tr}^{(k)}(t)} = {\sum\limits_{j}{\left( {- 1} \right)^{f_{j}^{(k)}}a_{j}^{(k)}{\omega\left( {{{c_{j}^{(k)}t} - T_{j}^{(k)} - {\delta\quad d_{\lbrack{j/N_{S}}\rbrack}^{(k)}}},b_{j}^{(k)}} \right)}}}$where k is the index of a transmitter, j is the index of a pulse withinits pulse train, (−1) f_(j) ^((k)), a_(j) ^((k)), b_(j) ^((k)), c_(j)^((k)), and ω(t,b_(j) ^((k))) are the coded polarity, pulse amplitude,pulse type, pulse width, and normalized pulse waveform of the jth pulseof the kth transmitter, T_(j) ^((k)) is the coded time shift of the jthpulse of the kth transmitter, δ is the time shift added when thetransmitted symbol is 1 (instead of 0), d^((k)) is the data (i.e., 0or 1) transmitted by the kth transmitter, and N_(s) is the number ofpulses per symbol (e.g., bit). Similar expressions can be derived toaccommodate other proposed forms of modulation.

An alternative form of time-shift modulation can be described asOne-of-Many Position Modulation (OMPM). The OMPM approach, shown in FIG.4B, involves shifting a pulse to one of N possible modulation positionsabout a nominal coded (or uncoded) time position in response to aninformation signal, where N represents the number of possible states.For example, if N were four (4), two data bits of information could beconveyed. For further details regarding OMPM, see “Apparatus, System andMethod for One-of-Many Position Modulation in an Impulse RadioCommunication System,” U.S. patent application Ser. No. 09/875,290,filed Jun. 7, 2001, assigned to the assignee of the present invention,and incorporated herein by reference.

An impulse radio communications system can employ flip modulationtechniques to convey information. The simplest flip modulation techniqueinvolves transmission of a pulse or an inverted (or flipped) pulse torepresent a data bit of information, as depicted in FIG. 4C. Flipmodulation techniques may also be combined with time-shift modulationtechniques to create two, four, or more different data states. One suchflip with shift modulation technique is referred to as Quadrature FlipTime Modulation (QFTM). The QFTM approach is illustrated in FIG. 4D.Flip modulation techniques are further described in patent applicationtitled “Apparatus, System and Method for Flip Modulation in an ImpulseRadio Communication System,” application Ser. No. 09/537,692, filed Mar.29, 2000, assigned to the assignee of the present invention, andincorporated herein by reference.

Vector modulation techniques may also be used to convey information.Vector modulation includes the steps of generating and transmitting aseries of time-modulated pulses, each pulse delayed by one of at leastfour pre-determined time delay periods and representative of at leasttwo data bits of information, and receiving and demodulating the seriesof time-modulated pulses to estimate the data bits associated with eachpulse. Vector modulation is shown in FIG. 4E. Vector modulationtechniques are further described in patent application titled “VectorModulation System and Method for Wideband Impulse Radio Communications,”application Ser. No. 09/169,765, filed Dec. 9, 1999, assigned to theassignee of the present invention, and incorporated herein by reference.

Reception and Demodulation

Impulse radio systems operating within close proximity to each other maycause mutual interference. While coding minimizes mutual interference,the probability of pulse collisions increases as the number ofcoexisting impulse radio systems rises. Additionally, various othersignals may be present that cause interference. Impulse radios canoperate in the presence of mutual interference and other interferingsignals, in part because they do not depend on receiving everytransmitted pulse. Impulse radio receivers perform a correlating,synchronous receiving function (at the RF level) that uses statisticalsampling and combining, or integration, of many pulses to recovertransmitted information. Typically, 1 to 1000 or more pulses areintegrated to yield a single data bit thus diminishing the impact ofindividual pulse collisions, where the number of pulses that must beintegrated to successfully recover transmitted information depends on anumber of variables including pulse rate, bit rate, range andinterference levels.

Interference Resistance

Besides providing channelization and energy smoothing, coding makesimpulse radios highly resistant to interference by enablingdiscrimination between intended impulse transmissions and interferingtransmissions. This property is desirable since impulse radio systemsmust share the energy spectrum with conventional radio systems and withother impulse radio systems.

FIG. 5A illustrates the result of a narrow band sinusoidal interferencesignal 502 overlaying an impulse radio signal 504. At the impulse radioreceiver, the input to the cross correlation would include the narrowband signal 502 and the received ultrawide-band impulse radio signal504. The input is sampled by the cross correlator using a templatesignal 506 positioned in accordance with a code. Without coding, thecross correlation would sample the interfering signal 502 with suchregularity that the interfering signals could cause interference to theimpulse radio receiver. However, when the transmitted impulse signal iscoded and the impulse radio receiver template signal 506 is synchronizedusing the identical code, the receiver samples the interfering signalsnon-uniformly. The samples from the interfering signal add incoherently,increasing roughly according to the square root of the number of samplesintegrated. The impulse radio signal samples, however, add coherently,increasing directly according to the number of samples integrated. Thus,integrating over many pulses overcomes the impact of interference.

Processing Gain

Impulse radio systems have exceptional processing gain due to their widespreading bandwidth. For typical spread spectrum systems, the definitionof processing gain, which quantifies the decrease in channelinterference when wide-band communications are used, is the ratio of thebandwidth of the channel to the bit rate of the information signal. Forexample, a direct sequence spread spectrum system with a 10 KHzinformation bandwidth and a 10 MHz channel bandwidth yields a processinggain of 1000, or 30 dB. However, far greater processing gains areachieved by impulse radio systems, where the same 10 KHz informationbandwidth is spread across a much greater 2 GHz channel bandwidth,resulting in a theoretical processing gain of 200,000, or 53 dB.

Capacity

It can be shown theoretically, using signal-to-noise arguments, thatthousands of simultaneous channels are available to an impulse radiosystem as a result of its exceptional processing gain.

The average output signal-to-noise ratio of the impulse radio may becalculated for randomly selected time-hopping codes as a function of thenumber of active users, N_(u), as:${{SNR}_{out}\left( N_{u} \right)} = \frac{\left( {N_{s}A_{1}m_{p}} \right)^{2}}{\sigma_{rec}^{2} + {N_{s}\sigma_{a}^{2}{\sum\limits_{k = 2}^{N_{u}}A_{k}^{2}}}}$where N_(s) is the number of pulses integrated per bit of information,A_(k) models the attenuation of transmitter k's signal over thepropagation path to the receiver, and σ_(rec) ² is the variance of thereceiver noise component at the pulse train integrator output. Themonocycle waveform-dependent parameters m_(p) and σ_(a) ² are given bym_(p) = ∫_(−∞)^(∞)ω(t)[ω(t) − ω(t − δ)]𝕕t andσ_(a)² = T_(f)⁻¹∫_(−∞)^(∞)[∫_(−∞)^(∞)ω(t − s)υ(t)𝕕t]²𝕕s,where ω(t) is the monocycle waveform, u(t)=ω(t)−ω(t−δ) is the templatesignal waveform, δ is the time shift between the monocycle waveform andthe template signal waveform, T_(f) is the pulse repetition time, and sis signal.

Multipath and Propagation

One of the advantages of impulse radio is its resistance to multipathfading effects. Conventional narrow band systems are subject tomultipath through the Rayleigh fading process, where the signals frommany delayed reflections combine at the receiver antenna according totheir seemingly random relative phases resulting in possible summationor possible cancellation, depending on the specific propagation to agiven location. Multipath fading effects are most adverse where a directpath signal is weak relative to multipath signals, which represents themajority of the potential coverage area of a radio system. In a mobilesystem, received signal strength fluctuates due to the changing mix ofmultipath signals that vary as its position varies relative to fixedtransmitters, mobile transmitters and signal-reflecting surfaces in theenvironment.

Impulse radios, however, can be substantially resistant to multipatheffects. Impulses arriving from delayed multipath reflections typicallyarrive outside of the correlation time and, thus, may be ignored. Thisprocess is described in detail with reference to FIGS. 5B and 5C. FIG.5B illustrates a typical multipath situation, such as in a building,where there are many reflectors 504B, 505B. In this figure, atransmitter 506B transmits a signal that propagates along three paths,the direct path 501B, path 1 502B, and path2 503B, to a receiver 508B,where the multiple reflected signals are combined at the antenna. Thedirect path 501B, representing the straight-line distance between thetransmitter and receiver, is the shortest. Path 1 502B represents amultipath reflection with a distance very close to that of the directpath. Path 2 503B represents a multipath reflection with a much longerdistance. Also shown are elliptical (or, in space, ellipsoidal) tracesthat represent other possible locations for reflectors that wouldproduce paths having the same distance and thus the same time delay.

FIG. 5C illustrates the received composite pulse waveform resulting fromthe three propagation paths 501B, 502B, and 503B shown in FIG. 5B. Inthis figure, the direct path signal 501B is shown as the first pulsesignal received. The path 1 and path 2 signals 502B, 503B comprise theremaining multipath signals, or multipath response, as illustrated. Thedirect path signal is the reference signal and represents the shortestpropagation time. The path 1 signal is delayed slightly and overlaps andenhances the signal strength at this delay value. The path 2 signal isdelayed sufficiently that the waveform is completely separated from thedirect path signal. Note that the reflected waves are reversed inpolarity. If the correlator template signal is positioned such that itwill sample the direct path signal, the path 2 signal will not besampled and thus will produce no response. However, it can be seen thatthe path 1 signal has an effect on the reception of the direct pathsignal since a portion of it would also be sampled by the templatesignal. Generally, multipath signals delayed less than one quarter wave(one quarter wave is about 1.5 inches, or 3.5 cm at 2 GHz centerfrequency) may attenuate the direct path signal. This region isequivalent to the first Fresnel zone in narrow band systems. Impulseradio, however, has no further nulls in the higher Fresnel zones. Thisability to avoid the highly variable attenuation from multipath givesimpulse radio significant performance advantages.

FIGS. 5D, 5E, and 5F represent the received signal from a TM-UWBtransmitter in three different multipath environments. These figures areapproximations of typical signal plots. FIG. 5D illustrates the receivedsignal in a very low multipath environment. This may occur in a buildingwhere the receiver antenna is in the middle of a room and is arelatively short, distance, for example, one meter, from thetransmitter. This may also represent signals received from a largerdistance, such as 100 meters, in an open field where there are noobjects to produce reflections. In this situation, the predominant pulseis the first received pulse and the multipath reflections are too weakto be significant. FIG. 5E illustrates an intermediate multipathenvironment. This approximates the response from one room to the next ina building. The amplitude of the direct path signal is less than in FIG.5D and several reflected signals are of significant amplitude. FIG. 5Fapproximates the response in a severe multipath environment such aspropagation through many rooms, from corner to corner in a building,within a metal cargo hold of a ship, within a metal truck trailer, orwithin an intermodal shipping container. In this scenario, the main pathsignal is weaker than in FIG. 5E. In this situation, the direct pathsignal power is small relative to the total signal power from thereflections.

An impulse radio receiver can receive the signal and demodulate theinformation using either the direct path signal or any multipath signalpeak having sufficient signal-to-noise ratio. Thus, the impulse radioreceiver can select the strongest response from among the many arrivingsignals. In order for the multipath signals to cancel and produce a nullat a given location, dozens of reflections would have to be cancelledsimultaneously and precisely while blocking the direct path, which is ahighly unlikely scenario. This time separation of mulitipath signalstogether with time resolution and selection by the receiver permit atype of time diversity that virtually eliminates cancellation of thesignal. In a multiple correlator rake receiver, performance is furtherimproved by collecting the signal power from multiple signal peaks foradditional signal-to-noise performance.

Where the system of FIG. 5B is a narrow band system and the delays aresmall relative to the data bit time, the received signal is a sum of alarge number of sine waves of random amplitude and phase. In theidealized limit, the resulting envelope amplitude has been shown tofollow a Rayleigh probability distribution as follows:${p(r)} = {\frac{r}{\sigma^{2}}{\exp\left( \frac{- r^{2}}{2\sigma^{2}} \right)}}$where r is the envelope amplitude of the combined multipath signals, andσ(2)^(1/2) is the RMS power of the combined multipath signals. TheRayleigh distribution curve in FIG. 5G shows that 10% of the time, thesignal is more than 10 dB attenuated. This suggests that 10 dB fademargin is needed to provide 90% link availability. Values of fade marginfrom 10 to 40 dB have been suggested for various narrow band systems,depending on the required reliability. This characteristic has been thesubject of much research and can be partially improved by suchtechniques as antenna and frequency diversity, but these techniquesresult in additional complexity and cost.

In a high multipath environment such as inside homes, offices,warehouses, automobiles, trailers, shipping containers, or outside in anurban canyon or other situations where the propagation is such that thereceived signal is primarily scattered energy, impulse radio systems canavoid the Rayleigh fading mechanism that limits performance of narrowband systems, as illustrated in FIGS. 5H and 5I. FIG. 5H depicts animpulse radio system in a high multipath environment 500H consisting ofa transmitter 506H and a receiver 508H. A transmitted signal follows adirect path 501H and reflects off reflectors 503H via multiple paths502H. FIG. 5I illustrates the combined signal received by the receiver508H over time with the vertical axis being signal strength in volts andthe horizontal axis representing time in nanoseconds. The direct path501H results in the direct path signal 502I while the multiple paths502H result in multipath signals 504I. In the same manner describedearlier for FIGS. 5B and 5C, the direct path signal 502I is sampled,while the multipath signals 504I are not, resulting in Rayleigh fadingavoidance.

Distance Measurement and Positioning

Impulse systems can measure distances to relatively fine resolutionbecause of the absence of ambiguous cycles in the received waveform.Narrow band systems, on the other hand, are limited to the modulationenvelope and cannot easily distinguish precisely which RF cycle isassociated with each data bit because the cycle-to-cycle amplitudedifferences are so small they are masked by link or system noise. Sincean impulse radio waveform has no multi-cycle ambiguity, it is possibleto determine waveform position to less than a wavelength, potentiallydown to the noise floor of the system. This time position measurementcan be used to measure propagation delay to determine link distance to ahigh degree of precision. For example, 30 ps of time transfer resolutioncorresponds to approximately centimeter distance resolution. See, forexample, U.S. Pat. No. 6,133,876, issued Oct. 17, 2000, titled “Systemand Method for Position Determination by Impulse Radio,” and U.S. Pat.No. 6,111,536, issued Aug. 29, 2000, titled “System and Method forDistance Measurement by Inphase and Quadrature Signals in a RadioSystem,” both of which are incorporated herein by reference.

In addition to the methods articulated above, impulse radio technologyalong with Time Division Multiple Access algorithms and Time Domainpacket radios can achieve geo-positioning capabilities in a radionetwork. This geo-positioning method is described in co-owned,co-pending U.S. Pat. No. 6,300,903 entitled “System and Method forPerson or Object Position Location Utilizing Impulse Radio,” which isincorporated herein by reference.

Power Control

Power control systems comprise a first transceiver that transmits animpulse radio signal to a second transceiver. A power control update iscalculated according to a performance measurement of the signal receivedat the second transceiver. The transmitter power of either transceiver,depending on the particular setup, is adjusted according to the powercontrol update. Various performance measurements are employed tocalculate a power control update, including bit error rate,signal-to-noise ratio, and received signal strength, used alone or incombination. Interference is thereby reduced, which may improveperformance where multiple impulse radios are operating in closeproximity and their transmissions interfere with one another. Reducingthe transmitter power of each radio to a level that producessatisfactory reception increases the total number of radios that canoperate in an area without saturation. Reducing transmitter power alsoincreases transceiver efficiency.

For greater elaboration of impulse radio power control, see U.S. Pat.No. 6,539,213 which is entitled “System and Method for Impulse RadioPower Control,” and is incorporated herein by reference.

Mitigating Effects of Interference

A method for mitigating interference in impulse radio systems comprisesthe steps of conveying the message in packets, repeating conveyance ofselected packets to make up a repeat package, and conveying the repeatpackage a plurality of times at a repeat period greater than twice theperiod of occurrence of the interference. The communication may convey amessage from a proximate transmitter to a distal receiver, and receive amessage by a proximate receiver from a distal transmitter. In such asystem, the method comprises the steps of providing interferenceindications by the distal receiver to the proximate transmitter, usingthe interference indications to determine predicted noise periods, andoperating the proximate transmitter to convey the message according toat least one of the following: (1) avoiding conveying the message duringnoise periods, (2) conveying the message at a higher power during noiseperiods, (3) increasing error detection coding in the message duringnoise periods, (4) re-transmitting the message following noise periods,(5) avoiding conveying the message when interference is greater than afirst strength, (6) conveying the message at a higher power when theinterference is greater than a second strength, (7) increasing errordetection coding in the message when the interference is greater than athird strength, and (8) re-transmitting a portion of the message afterinterference has subsided to less than a predetermined strength.

For greater elaboration of mitigating interference in impulse radiosystems, see the patent application titled “Method for MitigatingEffects of Interference in Impulse Radio Communication,” applicationSer. No. 09/587,033, filed Jun. 2, 1999, assigned to the assignee of thepresent invention, and incorporated herein by reference.

Moderating Interference in Equipment Control Applications

Yet another improvement to impulse radio includes moderatinginterference with impulse radio wireless control of an appliance. Thecontrol is affected by a controller remote from the appliance whichtransmits impulse radio digital control signals to the appliance. Thecontrol signals have a transmission power and a data rate. The methodcomprises the steps of establishing a maximum acceptable noise value fora parameter relating to interfering signals and a frequency range formeasuring the interfering signals, measuring the parameter for theinterference signals within the frequency range, and effecting analteration of transmission of the control signals when the parameterexceeds the maximum acceptable noise value.

For greater elaboration of moderating interference while effectingimpulse radio wireless control of equipment, see U.S. Pat. No. 6,571,089which is entitled “Method and Apparatus for Moderating InterferenceWhile Effecting Impulse Radio Wireless Control of Equipment,” and isincorporated herein by reference.

Exemplary Transceiver Implementation

Transmitter

An exemplary embodiment of an impulse radio transmitter 602 of animpulse radio communication system having an optional subcarrier channelwill now be described with reference to FIG. 6.

The transmitter 602 comprises a time base 604 that generates a periodictiming signal 606. The time base 604 typically comprises a voltagecontrolled oscillator (VCO), or the like, having a high timing accuracyand low jitter, on the order of picoseconds (ps). The control voltage toadjust the VCO center frequency is set at calibration to the desiredcenter frequency used to define the transmitter's nominal pulserepetition rate. The periodic timing signal 606 is supplied to aprecision timing generator 608.

The precision timing generator 608 supplies synchronizing signals 610 tothe code source 612 and utilizes the code source output 614, togetherwith an optional, internally generated subcarrier signal, and aninformation signal 616, to generate a modulated, coded timing signal618.

An information source 620 supplies the information signal 616 to theprecision timing generator 608. The information signal 616 can be anytype of intelligence, including digital bits representing voice, data,imagery, or the like, analog signals, or complex signals.

A pulse generator 622 uses the modulated, coded timing signal 618 as atrigger signal to generate output pulses. The output pulses are providedto a transmit antenna 624 via a transmission line 626 coupled thereto.The output pulses are converted into propagating electromagnetic pulsesby the transmit antenna 624. The electromagnetic pulses are called theemitted signal, and propagate to an impulse radio receiver 702, such asshown in FIG. 7, through a propagation medium. In a preferredembodiment, the emitted signal is wide-band or ultrawide-band,approaching a monocycle pulse as in FIG. 1B. However, the emitted signalmay be spectrally modified by filtering of the pulses, which may causethem to have more zero crossings (more cycles) in the time domain,requiring the radio receiver to use a similar waveform as the templatesignal for efficient conversion.

Receiver

An exemplary embodiment of an impulse radio receiver (hereinafter calledthe receiver) for the impulse radio communication system is nowdescribed with reference to FIG. 7.

The receiver 702 comprises a receive antenna 704 for receiving apropagated impulse radio signal 706. A received signal 708 is input to across correlator or sampler 710, via a receiver transmission line,coupled to the receive antenna 704. The cross correlation 710 produces abaseband output 712.

The receiver 702 also includes a precision timing generator 714, whichreceives a periodic timing signal 716 from a receiver time base 718.This time base 718 may be adjustable and controllable in time,frequency, or phase, as required by the lock loop in order to lock onthe received signal 708. The precision timing generator 714 providessynchronizing signals 720 to the code source 722 and receives a codecontrol signal 724 from the code source 722. The precision timinggenerator 714 utilizes the periodic timing signal 716 and code controlsignal 724 to produce a coded timing signal 726. The template generator728 is triggered by this coded timing signal 726 and produces a train oftemplate signal pulses 730 ideally having waveforms substantiallyequivalent to each pulse of the received signal 708. The code forreceiving a given signal is the same code utilized by the originatingtransmitter to generate the propagated signal. Thus, the timing of thetemplate pulse train matches the timing of the received signal pulsetrain, allowing the received signal 708 to be synchronously sampled inthe correlator 710. The correlator 710 preferably comprises a multiplierfollowed by a short term integrator to sum the multiplier product overthe pulse interval.

The output of the correlator 710 is coupled to a subcarrier demodulator732, which demodulates the subcarrier information signal from theoptional subcarrier. The purpose of the optional subcarrier process,when used, is to move the information signal away from DC (zerofrequency) to improve immunity to low frequency noise and offsets. Theoutput of the subcarrier demodulator is then filtered or integrated inthe pulse summation stage 734. A digital system embodiment is shown inFIG. 7. In this digital system, a sample and hold 736 samples the output735 of the pulse summation stage 734 synchronously with the completionof the summation of a digital bit or symbol. The output of sample andhold 736 is then compared with a nominal zero (or reference) signaloutput in a detector stage 738 to provide an output signal 739representing the digital state of the output voltage of sample and hold736.

The baseband signal 712 is also input to a lowpass filter 742 (alsoreferred to as lock loop filter 742). A control loop comprising thelowpass filter 742, time base 718, precision timing generator 714,template generator 728, and correlator 710 is used to generate an errorsignal 744. The error signal 744 provides adjustments to the adjustabletime base 718 to position in time the periodic timing signal 726 inrelation to the position of the received signal 708.

In a transceiver embodiment, substantial economy can be achieved bysharing part or all of several of the functions of the transmitter 602and receiver 702. Some of these include the time base 718, precisiontiming generator 714, code source 722, antenna 704, and the like.

FIGS. 8A-8C illustrate the cross correlation process and the correlationfunction. FIG. 8A shows the waveform of a template signal. FIG. 8B showsthe waveform of a received impulse radio signal at a set of severalpossible time offsets. FIG. 8C represents the output of the correlator(multiplier and short time integrator) for each of the time offsets ofFIG. 8B. Thus, this graph does not show a waveform that is a function oftime, but rather a function of time-offset. For any given pulsereceived, there is only one corresponding point that is applicable onthis graph. This is the point corresponding to the time offset of thetemplate signal used to receive that pulse. Further examples and detailsof precision timing can be found described in U.S. Pat. Nos. 5,677,927and 6,304,623 both of which are incorporated herein by reference.

Because of the unique nature of impulse radio receivers, severalmodifications have been recently made to enhance system capabilities.Modifications include the utilization of multiple correlators to measurethe impulse response of a channel to the maximum communications range ofthe system and to capture information on data symbol statistics.Further, multiple correlators enable rake pulse correlation techniques,more efficient acquisition and tracking implementations, variousmodulation schemes, and collection of time-calibrated pictures ofreceived waveforms. For greater elaboration of multiple correlatortechniques, see patent application titled “System and Method of usingMultiple Correlator Receivers in an Impulse Radio System”, applicationSer. No. 09/537,264, filed Mar. 29, 2000, assigned to the assignee ofthe present invention, and incorporated herein by reference.

Methods to improve the speed at which a receiver can acquire and lockonto an incoming impulse radio signal have been developed. In oneapproach, a receiver includes an adjustable time base to output asliding periodic timing signal having an adjustable repetition rate anda decode timing modulator to output a decode signal in response to theperiodic timing signal. The impulse radio signal is cross-correlatedwith the decode signal to output a baseband signal. The receiverintegrates T samples of the baseband signal and a threshold detectoruses the integration results to detect channel coincidence. A receivercontroller stops sliding the time base when channel coincidence isdetected. A counter and extra count logic, coupled to the controller,are configured to increment or decrement the address counter by one ormore extra counts after each T pulses is reached in order to shift thecode modulo for proper phase alignment of the periodic timing signal andthe received impulse radio signal. This method is described in moredetail in U.S. Pat. No. 5,832,035 to Fullerton, incorporated herein byreference.

In another approach, a receiver obtains a template pulse train and areceived impulse radio signal. The receiver compares the template pulsetrain and the received impulse radio signal. The system performs athreshold check on the comparison result. If the comparison resultpasses the threshold check, the system locks on the received impulseradio signal. The system may also perform a quick check, asynchronization check, and/or a command check of the impulse radiosignal. For greater elaboration of this approach, see U.S. Pat. No.6,556,621 which is entitled “Method and System for Fast Acquisition ofUltra Wideband Signals,” and is incorporated herein by reference.

A receiver has been developed that includes a baseband signal converterdevice and combines multiple converter circuits and an RF amplifier in asingle integrated circuit package. For greater elaboration of thisreceiver, see U.S. Pat. No. 6,421,389 entitled “Baseband SignalConverter for a Wideband Impulse Radio Receiver,” which is assigned tothe assignee of the present invention, and incorporated herein byreference.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

Referring to FIGS. 9-25, there are disclosed several embodiments of anexemplary system 900, an exemplary robot 902 and preferred method 1300in accordance with the present invention. Although the present inventionis described as using impulse radio technology, it should be understoodthat the present invention can be used with any type of ultra widebandtechnology, but is especially suited for use with time-modulated ultrawideband technology. Accordingly, the system 900, the robot 902 and thepreferred method 1300 should not be construed in a limited manner.

Referring to FIG. 9, there is a diagram illustrating the basiccomponents of the system 900 in accordance with the present invention.The system 900 includes a control station 904 that has a first impulseradio unit 906 which operates to transmit and receive impulse radiosignals 908 to and from a second impulse radio unit 910 attached to therobot 902 (only one shown). The impulse radio signals 908 conveyinformation using a known pseudorandom sequence of pulses that look likea series of Gaussian waveforms (see FIGS. 1-3). As described in greaterdetail below, the control station 904 can effectively control theactions of the robot 902 by using the information within in the impulseradio signals 908 transmitted to and receive from the robot 902. Inparticular, the control station 904 and robot 902 can use impulse radiotechnology and the information within in the impulse radio signals 908to effectively monitor and control, if needed, the environment within abuilding (other applications are described below). To accomplish thesetasks, the control station 904 and robot 902 utilize the revolutionaryand highly scalable communication capabilities, position capabilities(optional) and radar capabilities (optional) of impulse radiotechnology.

In other words, the control station 904 and robot 902 can use impulseradio signals 908 to transmit and receive information to and from oneanother in places and situations not possible with standard radiosignals. Again, the conventional radio technology used to transmit andreceive radio signals between a control station and robot within abuilding suffer from the adverse affects of “dead zones” and “multipathinterference”. Dead zones in a building make it difficult for a controlstation to maintain contact with a moving robot using standard radiosignals. For instance, the standard radio signals sent from the standardradio transceiver attached to the control station may not be able topenetrate a certain wall or floor within the building and as such maynot reach the standard radio transceiver attached to the moving robot.Fortunately in the present invention, the impulse radio signals 908transmitted between a robot 902 and control station 904 are located veryclose to DC which makes the attenuation due to walls and floors minimalwhen compared to standard radio signals.

In addition, “multipath interference” which is very problematic withinthe closed structure of a building can be caused by the interference ofa standard radio signal that has reached either the traditional robot ortraditional control station by two or more paths. Essentially, astandard radio receiver attached to a robot may not be able todemodulate a radio signal because the originally transmitted radiosignal effectively cancels itself out by bouncing of walls and floors ofthe building before reaching the robot and vice versa. The presentinvention is not affected by “multipath interference” because theimpulses of the impulse radio signals 908 delayed by multipathreflections typically arrive outside a correlation (or demodulation)period of the receiving impulse radio unit.

Moreover, traditional control stations use either standard radio orinfrared electromagnetic waves to transfer data to and from atraditional robot. However, these traditional communication means imposeundesirable limits on range, data rate and communication quality. Forinstance, traditional wireless communication technologies suffer fromthe following undesirable characteristics:

-   -   A limited spectral bandwidth.    -   A shared broadcast medium.    -   Are unprotected from outside signals.

In contrast, the use of impulse radio technology in the presentinvention provides many advantages over traditional wirelesscommunication technologies including, for example, the following:

-   -   Ultra-short duration pulses which yield ultrawide bandwidth        signals.    -   Extremely low power spectral densities.    -   Excellent immunity to interference from other radio systems.    -   Consumes substantially less power than conventional radios.    -   Capable of high bandwidth and multi-channel performance.

Referring to FIG. 10, there is a diagram illustrating in greater detailthe components of the control station 904 and the robot 902 shown inFIG. 9. As illustrated, the control station 904 incorporates the firstimpulse radio unit 906 and the robot 902 incorporates the second impulseradio unit 910. Each impulse radio unit 906 and 910 can be configured asa transceiver and include a receiving impulse radio unit 602 and atransmitting impulse radio unit 702 (see FIGS. 6 and 7). In thealternative, the impulse radio units 906 and 910 can be configured as areceiver or transmitter depending on the functional requirements of thecontrol station 904 and robot 902. For instance, the robot 902 may onlyneed to download operating instructions and, as such, the first impulseradio unit 906 could be a transmitting impulse radio unit and the secondimpulse radio unit 910 would be a receiving impulse radio unit. Again,the control station 904 and robot 902 use impulse radio signals 908 totransmit and receive information to and from one another in places andsituations not possible with standard radio signals.

In addition to enabling communications between the robot 902 and thecontrol station 904, impulse radio technology can also enable thecontrol station 904 to track the position of the robot 902 which has amovable platform 903. Of course, a control station 904 that knows thecurrent position of a robot 902 can better control the actions of thatrobot 902. To determine the current position of the robot 902, theimpulse radio unit 910 associated with the robot 902 interacts with oneor more reference impulse radio units 1002 (see FIG. 11) such thateither the robot 902, the control station 904, or one of the referenceimpulse radio units 1002 can calculate the current position of the robot902. How the impulse radio units 906 and 910 interact with one anotherto determine the position of the robot 902 can best be understood byreferring to the description associated with FIGS. 11 and 14-25.

The robot 902 may also carry one or more sensors 1006. For instance, thesensor 1006 could be a video camera 1006 a that can obtain informationin video form about the area surrounding the robot 902. This videoinformation can then be transmitted to the control station 904 using theimpulse radio unit 910 which modulates and forwards the informationusing high bandwidth impulse radio signals 908. As will be described ingreater detail below with respect to FIGS. 11, there can be a widevariety of sensors 1006 that can interact with and be controlled by theremote control station 904 in order to effectively monitor and control,if need, the environment within a building.

Referring to FIG. 11, there is a diagram illustrating the robot 902 andcontrol station 904 of FIG. 10 that can be used in a manner to monitorand control, if needed, the environment within a building 1102. Asillustrated, the building 1102 (shown as an industrial facility)includes a first floor 1104 and a second floor 1106. The first floor1104 can include a reception area 1108, restrooms 1110, dining hall1112, equipment room 1114, security control center 1116 and a shop area1118. The second floor 1106 can includes a series of offices 1120,conference room 1122 and restrooms 1124. Of course, the illustratedlayout of the building 1102 is for purposes of discussion only and isnot intended as a limitation to the present invention.

The robot 902 includes one or more sensors 1006 that are remotelycontrolled by the control station 904 in a manner that allows one tomonitor and control, if needed, the environment within a building 1102.The sensors 1006 can have many functions and can use many differenttechniques to obtain sensor related information which is eventuallymodulated and forwarded in the impulse radio signals 908 towards thecontrol station 904 (see FIG. 9). For instance, the sensor 1006 can takethe form of a thermostat 1006 a which can be used to monitor and controlthe temperature in a particular area of the building 1102 where therobot 902 happens to be located. In this case, the sensor 1006 a and theimpulse radio unit 910 would operate together to transmit an impulseradio signal 908 having a known pseudorandom sequence of pulses thatlook like a series of Gaussian waveforms (see FIGS. 1-3) that conveyenvironmental related information towards the impulse radio unit 906attached to the control station 904. The control station 904 can use thereceived environmental related information (e.g., temperature readings)to control the heating and cooling equipment within the building 1102.As described below, the sensor 1006 (e.g., thermostat, smoke detector,surveillance camera, motion detector) of the present invention canmonitor and transmit within impulse radio signals 908 different types ofsensor related information including, for example, environmental relatedinformation, safety related information and surveillance relatedinformation.

In regards to safety related information, the sensor 1006 can take theform of a smoke detector 1006 b, a gas detector 1006 c (e.g., carbonmonoxide detector) or any other sensor that can detect a dangeroussubstance within the building 1102. For instance, the smoke detector1006 b and the impulse radio unit 910 would operate together to transmitan impulse radio signal 908 having a known pseudorandom sequence ofpulses that look like a series of Gaussian waveforms (see FIGS. 1-3)that convey safety related information towards the impulse radio unit906 attached to the control station 904. In this example, the controlstation 904 is shown to be located in the security control center 1116.It should be understood that the control station 904 need not be locatedwithin the building 1102. Instead, the control station 904 can belocated in another building (not shown) and can interact with the robot902 via a telephone line and modem.

In regards to surveillance related information, the sensor 1006 can takethe form of a surveillance camera 1006 d, a motion detector 1006 e orany other sensor that can monitor an area outside or within the building1102. For instance, the surveillance camera 1006 d and the impulse radiounit 910 would operate together to transmit impulse radio signals 908having a known pseudorandom sequence of pulses that look like a seriesof Gaussian waveforms (see FIGS. 1-3) that convey surveillance relatedinformation to the impulse radio unit 906 attached to the controlstation 904. The control station 904 can be located in the securitycontrol center 1116 and include a display 1126 containing an overlayshowing the video taken by the surveillance camera 1006 d. In addition,the robot 902 could be capable of receiving impulse radio signals 908from the control station 904 that control the focus and movement of thesurveillance camera 1006 d. In another application, the motion detector1006 e (or impulse radio unit 910) can use the radar capabilities ofimpulse radio technology to detect the presence of a person (e.g.,intruder) and transmit this surveillance related information in impulseradio signals 908 to the control station 904. In fact, the impulse radiounit 910 can use the radar capabilities of impulse radio technology todetect the presence of a person (e.g., intruder) through a wall, flooror in areas not normally seen with the naked eye.

In regards to environmental related information, the sensor 1006 cantake the form of a thermostat 1006 a, a humidity detector 1006 f, a dustdetector 1006 g or any other sensor that can monitor an environmentalcondition within the building 1102. For instance, the humidity detector1006 f and the impulse radio unit 910 would operate together to transmitimpulse radio signals 908 having a known pseudorandom sequence of pulsesthat look like a series of Gaussian waveforms (see FIGS. 1-3) thatconvey environmental related information to the impulse radio unit 906attached to a control station 904. The control station 904 attached tothe dehumidifier/humidifier equipment can use the received environmentalrelated information (e.g., humidity readings) to control the humiditywithin the building 1102.

As described above, the sensors 1006 can monitor a variety of conditionswithin the building 1102 and modulate and forward the information usingimpulse radio signals 908 to the control station 904. In fact, thecontrol station 904 can be programmed to sound an alarm for buildingpersonnel whenever a monitored condition falls outside a predeterminedrange of acceptable conditions. In addition, the control station 904 cancause the sensor 1006 (e.g., smoke detectors 1006 b) to sound an alarmwhenever a monitored condition falls outside a predetermined range ofacceptable conditions. Moreover, the control station 904 can remotelyactivate and control a particular sensor 1006 to monitor the environmentwith the building 1102.

The robot 902 may also include an interface unit 1128 (e.g., speaker,microphone) which enables two-way communications between the monitoringpersonnel at the control station 904 and people in the vicinity of therobot 902. The interface unit 1128 can include a display 1130 thatenables the people in the vicinity of the robot 902 to view a variety ofinformation including monitored information from the sensors 1006 andmonitored vehicular parameter(s) (if any) of the robot 902.

The control station 904 may also interact with an Internet site 1132 andprovide the current positions of the robots 902 within the building1102, the monitored information from the sensors 1006 and the monitoredvehicular parameter(s) of each robot 902. Thus, people (not shown) canuse the robots 902 to monitor and control the environment within thebuilding 1102. In other words, these people can control the actions ofthe robot 902 within the building.

To accomplish all of these tasks, the control station 904 needs to knowthe current position of a moving robot 902 and should also be able tocontrol the movement of the robot 902. As briefly discussed above, thecontrol station 904 can determine or at least be informed about thecurrent position of the robot 902 using the position capabilities ofimpulse radio technology. To determine the current position of the robot902, the impulse radio unit 910 associated with the robot 902 interactswith one or more reference impulse radio units 1002 (only eight shown inthe building 1102) such that either the robot 902, the control station904, or one of the reference impulse radio units 1002 can calculate thecurrent position of the robot 902.

The reference impulse radio units 1002 (only 8 shown) have knownpositions and are located to provide maximum coverage within thebuilding 1102. The control station 904 typically has a hardwireconnection but could have a wireless connection to the reference impulseradio units 1002. Each robot 902 (only two shown in FIG. 12) is capableof moving around within the building 1102 and interacting with one ormore of the reference impulse radio units 1002 such that either thecontrol station 904, the robot 902 or one of the reference impulse radiounits 1002 can calculate the current position of the robot 902. Avariety of impulse radio positioning networks (e.g., two or morereference impulse radio units 1002 and one or more robots 902) thatenable the present invention to perform the positioning and trackingfunctions are described in greater detail below with reference to FIGS.14-25.

For instance, the positioning and tracking functions can be accomplishedby stepping through several steps. The first step is for the referenceimpulse radio units 1002 to synchronize together and begin passinginformation. Then, when a robot 902 is powered-on or enters the building1102, it synchronizes itself to the previously synchronized referenceimpulse radio units 1002. Once the robot 902 is synchronized, it beginscollecting and time-tagging range measurements from any availablereference impulse radio units 1002. The robot 902 then takes thesetime-tagged ranges and, using a least squares-based or similarestimator, calculates its position within the building 1102.Alternatively, one of the reference impulse radio units 1002 cancalculate the position of the robot 902. Thereafter, the robot 902 orone of the reference impulse radio units 1002 forwards its positioncalculation to the control station 904 for storage and/or real-timedisplay. It should be understood that the control station 904 can beprogrammed to track only the robot(s) 902 that the monitoring personnelwant to watch at one time.

Referring to FIG. 12, there is a diagram illustrating in greater detailthe robot and control station of FIG. 10 used in a manner to monitor andtrack physical assets 1200 within the building 1102. As illustrated, thephysical assets 1200 are located in the shop area 1118 of the building1102 but they could be located throughout the building 1102. Basically,the robot 902 can incorporate an identification reader 1202 that canreceive impulse radio signals 908 containing identification informationfrom wireless identification tags 1204 that are attached to physicalassets 1200. The identification information can be a basicidentification number that can be used to identify a particular physicalasset. As such, the identification reader 1202 coupled to the impulseradio unit 910 can use impulse radio technology to help buildingpersonnel at the control station 904 keep track of a wide array ofphysical assets 1200. Physical assets 1200 can include just about anvaluable asset including, for example, commercial goods, military goods,artwork, computers, cash drawers.

In addition to keeping track of physical assets 1200, the robot 902 andthe identification reader 1202 can use the positioning capabilities ofimpulse radio technology to locate each physical asset 1200. One way, todetermine the position of each physical asset 1200 would be to use thepositioning process described above wherein the reference impulse radiounits 1002 would interact with the wireless identification tags 1204 onthe physical assets 1200. This process of determining the position ofphysical assets 1200 is very similar to the process of determining theposition of the robot 902 within the building 1102.

Another way, to determine the position of each physical asset 1200 wouldbe to enable the robot 902 itself to determine the position of eachasset 1200. For instance, a robot 902 including the identificationreader 1202 could take multiple range measurements (e.g., measuringsignal strength) of each wireless identification tag 1204 as it moveswithin the building 1102, which enables a trilateration capability ofthe robot 902 to more precisely locate each wireless identification tag1204 on each physical asset 1200.

Alternatively, the robot 902 can move and attempt to locate a particularphysical asset 1200. This capability would typically require a two-waywireless identification tag 1204 in order to be able to perform thehalf-duplex ranging function at the robot 902. A two-way wirelessidentification tag 1204 would include a transmitting impulse radio unit702 and a receiving impulse radio unit 602 (see FIGS. 6 and 7). Ofcourse, the two-way wireless identification tag 1204 would have higherpower requirements than a transmit-only wireless identification tag1204. But, the battery life of the two-way wireless identification tag1204 would increase if the tag 1204 used a protocol referred to apseudo-transmit-only protocol. In this mode, the two-way wirelessidentification tag 1204 is normally in a sleep mode (neither listeningor transmitting) but periodically wakes-up to transmit identificationinformation at predetermined intervals and then receive transmissionsfrom the robot 902 for a short period of time following transmission ofthe identification information. In the receive mode, the two-waywireless identification tag 1204 would listen for range or statusrequests from the robot 902. The receive mode does use extra power notconsumed in a transmit-only tag, but it only needs to be in this modefor a few milliseconds. Normally, the two-way wireless identificationtag 1204 hears no response from the robot 902 and goes back to sleep.However, if the robot 902 needed to know the range to the two-waywireless identification tag 1204 or other status, it would initiate arange request that the two-way wireless identification tag 1204 hearsand then answers. Thus, this type of two-way wireless identification tag1204 has a power budget only a little worse than a transmit-onlywireless identification tag 1204.

Referring to FIG. 13, there is a flowchart illustrating the basic stepsof a preferred method 1300 for controlling the actions of a robot 902.Beginning at step 1302, the robot 902 is attached to the impulse radiounit 910 which typically includes an impulse radio transmitter 602 andan impulse radio receiver 702.

At step 1304, the robot 902 and impulse radio unit 910 would operatetogether to communicate with the control station 904 using impulse radiosignals 908 that contain information about the robot 902 and the areasurrounding the robot 902. Again, the control station 904 may be locatedin the same building 1102 as the robot 902 or it may be remotely locatedand still interact with and control the robot 902.

At step 1306, the control station 904 and monitoring personnel can thenuse the information conveyed in the impulse radio signals 908 to controlthe actions of the robot 902. For instance, the control station 904 canuse the conveyed information to control the actions of the robot 902 inorder to monitor and control, if needed, the environment within thebuilding 1102. The information obtained by the robot 902 and conveyed inimpulse radio signals 908 to the control station 904 can include a widevariety of information including, for example, environmental relatedinformation, safety related information, inventory related informationand surveillance related information.

At step 1308, the control station 904 can display all or a portion ofthe information received from the robot 902. Monitoring personnel canuse the displayed information to control the movements and actions ofthe robot 902. In particular, the control station 904 can use theconveyed information to control the actions of the robot 902 in order tomonitor and control, if needed, the environment within the building1102.

At step 1310, the control station 904 and monitoring personnel can useimpulse radio technology to establish communications with a person nearthe robot 902.

At step 1312, the control station 904 could use the positioningcapabilities of impulse radio technology to periodically determine aposition of each robot 902. Again, the control station 904 and a seriesof reference impulse radio units 1002 can operate together to determinethe position of a robot 902. In particular, the reference impulse radiounits 1002 have known positions and are located to provide maximumcoverage throughout the building 1102. Each robot 902 is capable ofinteracting with one or more of the reference impulse radio units 1002such that either the robot 902, the control station 904, or one of thereference impulse radio units 1002 is able to triangulate and calculatethe current position of a robot 902.

At step 1314, the robot 902 can use the radar capability of the impulseradio unit to detect a person (e.g., intruder) in the vicinity of therobot 902. It should be understood that the robot 902 can utilize on onechip (i.e., the impulse radio unit 910) the revolutionary positioncapabilities, radar capabilities and/or communication capabilities ofimpulse radio technology to perform the above-mentioned functions.Described below are some exemplary functions that can be performed bythe robot 902 which can take many different shapes including, forexample, a toy, a security robot, an industrial robot (i.e., welder,manufacturer . . . ) and a micro-airplane.

Impulse Radio Positioning Networks

A variety of impulse radio positioning networks capable of performingthe positioning and tracking functions of the present invention aredescribed in this Section (see also U.S. Pat. No. 6,300,903 B1 which isincorporated herein). An impulse radio positioning network includes aset of reference impulse radio units 1002 (shown below as referenceimpulse radio units R1-R6), one or more robots 902 (shown below asrobots M1-M3) and a control station 904.

Synchronized Transceiver Tracking Architecture

Referring to FIG. 14, there is illustrated a block diagram of an impulseradio positioning network 1400 utilizing a synchronized transceivertracking architecture. This architecture is perhaps the most generic ofthe impulse radio positioning networks since both robots M1 and M2 andreference impulse radio units R1-R4 are full two-way transceivers. Thenetwork 1400 is designed to be scalable, allowing from very few robotsM1 and M2 and reference impulse radio units R1-R4 to a very largenumber. This particular example of the synchronized transceiver trackingarchitecture shows a network 1400 of four reference impulse radio unitsR1-R4 and two robots M1 and M2. The arrows between the radios representtwo-way data and/or information links. A fully inter-connected networkwould have every radio continually communicating with every other radio,but this is not required and can be dependent upon the needs of theparticular application.

Each radio is a two-way transceiver; thus each link between radios istwo-way (duplex). Precise ranging information (the distance between tworadios) is distributed around the network 1400 in such a way as to allowthe robots M1 and M2 to determine their precise three-dimensionalposition within a local coordinate system. This position, along withother data or information traffic, can then be relayed from the robotsM1 and M2 back to the reference master impulse radio unit R1, one of theother reference relay impulse radio units R2-R4 or the control station904.

The radios used in this architecture are impulse radio two-waytransceivers. The hardware of the reference impulse radio units R1-R4and robots M1 and M2 is essentially the same. The firmware, however,varies slightly based on the functions each radio must perform. Forexample, the reference master impulse radio unit R1 directs the passingof information and is typically responsible for collecting all the datafor external graphical display at the control station 904. The remainingreference relay impulse radio units R2-R4 contain a separate version ofthe firmware, the primary difference being the different parameters orinformation that each reference relay impulse radio unit R2-R4 mustprovide the network. Finally, the robots M1 and M2 have their ownfirmware version that calculates their position.

In FIG. 14, each radio link is a two-way link that allows for thepassing of information, both data and/or information. The data-ratesbetween each radio link is a function of several variables including thenumber of pulses integrated to get a single bit, the number of bits perdata parameter, the length of any headers required in the messages, therange bin size, and the number of radios in the network.

By transmitting in assigned time slots and by carefully listening to theother radios transmit in their assigned transmit time slots, the entiregroup of radios within the network, both robots M1 and M2 and referenceimpulse radio units R1-R4, are able to synchronize themselves. Theoscillators used on the impulse radio boards drift slowly in time, thusthey may require continual monitoring and adjustment of synchronization.The accuracy of this synchronization process (timing) is dependent uponseveral factors including, for example, how often and how long eachradio transmits.

The purpose of this impulse radio positioning network 1400 is to enablethe tracking of the robots M1 and M2. Tracking is accomplished bystepping through several well-defined steps. The first step is for thereference impulse radio units R1-R4 to synchronize together and beginpassing information. Then, when a robot M1 or M2 enters the networkarea, it synchronizes itself to the previously synchronized referenceimpulse radio units R1-R4. Once the robot M1 or M2 is synchronized, itbegins collecting and time-tagging range measurements from any availablereference impulse radio units R1-R4 (or other robot M1 or M2). The robotM1 or M2 then takes these time-tagged ranges and, using a leastsquares-based or similar estimator, calculates the position of the robotM1 or M2 in local coordinates. If the situation warrants and theconversion possible, the local coordinates can be converted to any oneof the worldwide coordinates such as Earth Centered Inertial (ECI),Earth Centered Earth Fixed (ECEF), or J2000 (inertial coordinates fixedto year 2000). Finally, the robot M1 or M2 forwards its positioncalculation to the control station 904 for storage and real-timedisplay.

Unsynchronized Transceiver Tracking Architecture

Referring to FIG. 15, there is illustrated a block diagram of an impulseradio positioning network 1500 utilizing an unsynchronized transceivertracking architecture. This architecture is similar to synchronizedtransceiver tracking of FIG. 14, except that the reference impulse radiounits R1-R4 are not time-synchronized. Both the robots M1 and M2 andreference impulse radio units R1-R4 for this architecture are fulltwo-way transceivers. The network is designed to be scalable, allowingfrom very few robots M1 and M2 and reference impulse radio units R1-R4and to a very large number. This particular example of theunsynchronized transceiver tracking architecture shows a network 1500 offour reference impulse radio units R1-R4 and two robots M1 and M2. Thearrows between the radios represent two-way data and/or informationlinks. A fully inter-connected network would have every radiocontinually communicating with every other radio, but this is notrequired and can be defined as to the needs of the particularapplication.

Each radio is a two-way transceiver; thus each link between radios istwo-way (duplex). Precise ranging information (the distance between tworadios) is distributed around the network in such a way as to allow therobots M1 and M2 to determine their precise three-dimensional positionwithin a local coordinate system. This position, along with other dataor information traffic, can then be relayed from the robots M1 and M2back to the reference master impulse radio unit R1, one of the otherreference relay impulse radio units R2-R3 or the control station 904.

The radios used in the architecture of FIG. 15 are impulse radio two-waytransceivers. The hardware of the reference impulse radio units R1-R4and robots M1 and M2 is essentially the same. The firmware, however,varies slightly based on the functions each radio must perform. Forexample, the reference master impulse radio unit R1 directs the passingof information, and typically is responsible for collecting all the datafor external graphical display at the control station 904. The remainingreference relay impulse radio units R2-R4 contain a separate version ofthe firmware, the primary difference being the different parameters orinformation that each reference relay radio must provide the network.Finally, the robots M1 and M2 have their own firmware version thatcalculates their position and displays it locally if desired. In FIG.15, each radio link is a two-way link that allows for the passing ofinformation, data and/or information. The data-rates between each radiolink is a function of several variables including the number of pulsesintegrated to get a single bit, the number of bits per data parameter,the length of any headers required in the messages, the range bin size,and the number of radios in the network.

Unlike the radios in the synchronized transceiver tracking architecture,the reference impulse radio units R1-R4 in this architecture are nottime-synchronized as a network. These reference impulse radio unitsR1-R4 operate independently (free-running) and provide ranges to therobots M1 and M2 either periodically, randomly, or when tasked.Depending upon the application and situation, the reference impulseradio units R1-R4 may or may not talk to other reference radios in thenetwork.

As with the architecture of FIG. 14, the purpose of this impulse radiopositioning network 1500 is to enable the tracking of robots M1 and M2.Tracking is accomplished by stepping through several steps. These stepsare dependent upon the way in which the reference impulse radio unitsR1-R4 range with the robots M1 and M2 (periodically, randomly, or whentasked). When a robot M1 or M2 enters the network area, it eitherlistens for reference impulse radio units R1-R4 to broadcast, thenresponds, or it queries (tasks) the desired reference impulse radiounits R1-R4 to respond. The robot M1 or M2 begins collecting andtime-tagging range measurements from reference (or other mobile) radios.The robot M1 or M2 then takes these time-tagged ranges and, using aleast squares-based or similar estimator, calculates the position of therobot M1 or M2 in local coordinates. If the situation warrants and theconversion possible, the local coordinates can be converted to any oneof the worldwide coordinates such as Earth Centered Inertial (ECI),Earth Centered Earth Fixed (ECEF), or J2000 (inertial coordinates fixedto year 2000). Finally, the robot M1 or M2 forwards its positioncalculation to the control station 904 for storage and real-timedisplay.

Synchronized Transmitter Tracking Architecture

Referring to FIG. 16, there is illustrated a block diagram of an impulseradio positioning network 1600 utilizing a synchronized transmittertracking architecture. This architecture is perhaps the simplest of theimpulse radio positioning architectures, from the point-of-view of therobots M1 and M2, since the robots M1 and M2 simply transmit in afree-running sense. The network is designed to be scalable, allowingfrom very few robots M1 and M2 and reference impulse radio units R1-R4to a very large number. This architecture is especially applicable to an“RF tag” (radio frequency tag) type of application.

This particular example of synchronized transmitter trackingarchitecture shows a network 1600 of four reference impulse radio unitsradios R1-R4 and two robots M1 and M2. The arrows between the radiosrepresent two-way and one-way data and/or information links. Notice thatthe robots M1 and M2 only transmit, thus they do not receive thetransmissions from the other radios.

Each reference impulse radio unit R1-R4 is a two-way transceiver; thuseach link between reference impulse radio units R1-R4 is two-way(duplex). Precise ranging information (the distance between two radios)is distributed around the network in such a way as to allow thesynchronized reference impulse radio units R1-R4 to receivetransmissions from the robots M1 and M2 and then determine thethree-dimensional position of the robots M1 and M2. This position, alongwith other data or information traffic, can then be relayed fromreference relay impulse radio units R2-R4 back to the reference masterimpulse radio unit R1 or the control station 904.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the robots M1 and M2 are one-waytransmitters. The firmware in the radios varies slightly based on thefunctions each radio must perform. For example, the reference masterimpulse radio unit R1 is designated to direct the passing ofinformation, and typically is responsible for collecting all the datafor external graphical display at the control station 904. The remainingreference relay impulse radio units R2-R4 contain a separate version ofthe firmware, the primary difference being the different parameters orinformation that each reference relay impulse radio unit R2-R4 mustprovide the network. Finally, the robots M1 and M2 have their ownfirmware version that transmits pulses in predetermined sequences.

Each reference radio link is a two-way link that allows for the passingof information, data and/or information. The data-rates between eachradio link is a function of several variables including the number ofpulses integrated to get a single bit, the number of bits per dataparameter, the length of any headers required in the messages, the rangebin size, and the number of radios in the network.

By transmitting in assigned time slots and by carefully listening to theother radios transmit in their assigned transmit time slots, the entiregroup of reference impulse radio units R1-R4 within the network are ableto synchronize themselves. The oscillators used on the impulse radioboards drift slowly in time, thus they may require monitoring andadjustment to maintain synchronization. The accuracy of thissynchronization process (timing) is dependent upon several factorsincluding, for example, how often and how long each radio transmitsalong with other factors. The robots M1 and M2, since they aretransmit-only transmitters, are not time-synchronized to thesynchronized reference impulse radio units R1-R4.

The purpose of the impulse radio positioning network is to enable thetracking of robots M1 and M2. Tracking is accomplished by steppingthrough several well-defined steps. The first step is for the referenceimpulse radio units R1-R4 to synchronize together and begin passinginformation. Then, when a robot M1 or M2 enters the network area andbegins to transmit pulses, the reference impulse radio units R1-R4 pickup these pulses as time-of-arrivals (TOAs). Multiple TOAs collected bydifferent synchronized reference impulse radio units R1-R4 are thenconverted to ranges, which are then used to calculate the XYZ positionof the robot M1 or M2 in local coordinates. If the situation warrantsand the conversion possible, the local coordinates can be converted toany one of the worldwide coordinates such as Earth Centered Inertial(ECI), Earth Centered Earth Fixed (ECEF), or J2000 (inertial coordinatesfixed to year 2000). Finally, the reference impulse radio units R1-R4forwards their position calculation to the control station 904 forstorage and real-time display.

Unsynchronized Transmitter Tracking Architecture

Referring to FIG. 17, there is illustrated a block diagram of an impulseradio positioning network 1700 utilizing an unsynchronized transmittertracking architecture. This architecture is very similar to thesynchronized transmitter tracking architecture except that the referenceimpulse radio units R1-R4 are not synchronized in time. In other words,both the reference impulse radio units R1-R4 and the robots M1 and M2are free-running. The network is designed to be scalable, allowing fromvery few robots M1 and M2 and reference impulse radio units R1-R4 to avery large number. This architecture is especially applicable to an “RFtag” (radio frequency tag) type of application.

This particular example of the unsynchronized transmitter trackingarchitecture shows a network 1700 of four reference impulse radio unitsR1-R4 and two robots M1 and M2. The arrows between the radios representtwo-way and one-way data and/or information links. Notice that therobots M1 and M2 only transmit, thus they do not receive thetransmissions from the other radios. Unlike the synchronous transmittertracking architecture, the reference impulse radio units R1-R4 in thisarchitecture are free-running (unsynchronized). There are several waysto implement this design, the most common involves relaying thetime-of-arrival (TOA) pulses from the robots M1 and M2 and referenceimpulse radio units R1-R4, as received at the reference impulse radiounits R1-R4, back to the reference master impulse radio unit R1 whichcommunicates with the control station 904.

Each reference impulse radio unit R1-R4 in this architecture is atwo-way impulse radio transceiver; thus each link between referenceimpulse radio unit R1-R4 can be either two-way (duplex) or one-way(simplex). TOA information is typically transmitted from the referenceimpulse radio units R1-R4 back to the reference master impulse radiounit R1 where the TOAs are converted to ranges and then an XYZ positionof the robot M1 or M2, which can then be forwarded and displayed at thecontrol station 904.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the robots M1 and M2 are one-wayimpulse radio transmitters. The firmware in the radios varies slightlybased on the functions each radio must perform. For example, thereference master impulse radio R1 collects the TOA information, and istypically responsible for forwarding this tracking data to the controlstation 904. The remaining reference relay impulse radio units R2-R4contain a separate version of the firmware, the primary difference beingthe different parameters or information that each reference relayimpulse radio units R2-R4 must provide the network. Finally, the robotsM1 and M2 have their own firmware version that transmits pulses inpredetermined sequences.

Each reference radio link is a two-way link that allows for the passingof information, data and/or information. The data-rates between eachradio link is a function of several variables including the number ofpulses integrated to get a single bit, the number of bits per dataparameter, the length of any headers required in the messages, the rangebin size, and the number of radios in the network.

Since the reference impulse radio units R1-R4 and robots M1 and M2 arefree-running, synchronization is actually done by the reference masterimpulse radio unit R1. The oscillators used in the impulse radios driftslowly in time, thus they may require monitoring and adjustment tomaintain synchronization at the reference master impulse radio unit R1.The accuracy of this synchronization (timing) is dependent upon severalfactors including, for example, how often and how long each radiotransmits along with other factors.

The purpose of the impulse radio positioning network is to enable thetracking of robots M1 and M2. Tracking is accomplished by steppingthrough several steps. The most likely method is to have each referenceimpulse radio unit R1-R4 periodically (randomly) transmit a pulsesequence. Then, when a robot M1 or M2 enters the network area and beginsto transmit pulses, the reference impulse radio units R1-R4 pick upthese pulses as time-of-arrivals (TOAs) as well as the pulses (TOAs)transmitted by the other reference radios. TOAs can then either berelayed back to the reference master impulse radio unit R1 or justcollected directly (assuming it can pick up all the transmissions). Thereference master impulse radio unit R1 then converts these TOAs toranges, which are then used to calculate the XYZ position of the robotM1 or M2. If the situation warrants and the conversion possible, the XYZposition can be converted to any one of the worldwide coordinates suchas Earth Centered Inertial (ECI), Earth Centered Earth Fixed (ECEF), orJ2000 (inertial coordinates fixed to year 2000). Finally, the referencemaster impulse radio unit R1 forwards its position calculation to thecontrol station 904 for storage and real-time display.

Synchronized Receiver Tracking Architecture

Referring to FIG. 18, there is illustrated a block diagram of an impulseradio positioning network 1800 utilizing a synchronized receivertracking architecture. This architecture is different from thesynchronized transmitter tracking architecture in that in this designthe robots M1 and M2 determine their positions but are not able tobroadcast it to anyone since they are receive-only radios. The networkis designed to be scalable, allowing from very few robots M1 and M2 andreference impulse radio units R1-R4 to a very large number.

This particular example of the synchronized receiver trackingarchitecture shows a network 1800 of four reference impulse radio unitsR1-R4 and two robots M1 and M2. The arrows between the radios representtwo-way and one-way data and/or information links. Notice that therobots M1 and M2 receive transmissions from other radios, and do nottransmit.

Each reference impulse radio unit R1-R4 is a two-way transceiver, andeach robot M1 and M2 is a receive-only radio. Precise, synchronizedpulses are transmitted by the reference network and received by thereference impulse radio units R1-R4 and the robots M1 and M2. The robotsM1 and M2 take these times-of-arrival (TOA) pulses, convert them toranges, then determine their XYZ positions. Since the robots M1 and M2do not transmit, only they themselves know their XYZ positions.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the robots M1 and M2 arereceive-only radios. The firmware for the radios varies slightly basedon the functions each radio must perform. For example, the referencemaster impulse radio unit R1 is designated to direct the synchronizationof the reference radio network. The remaining reference relay impulseradio units R2-R4 contain a separate version of the firmware, theprimary difference being the different parameters or information thateach reference relay impulse radio unit R2-R4 must provide the network.Finally, the robots M1 and M2 have their own firmware version thatcalculates their position and displays it locally if desired.

Each reference radio link is a two-way link that allows for the passingof information, data and/or information. The robots M1 and M2 arereceive-only. The data-rates between each radio link is a function ofseveral variables including the number of pulses integrated to get asingle bit, the number of bits per data parameter, the length of anyheaders required in the messages, the range bin size, and the number ofradios in the network.

By transmitting in assigned time slots and by carefully listening to theother reference impulse radio units R1-R4 transmit in their assignedtransmit time slots, the entire group of reference impulse radio unitsR1-R4 within the network are able to synchronize themselves. Theoscillators used on the impulse radio boards may drift slowly in time,thus they may require monitoring and adjustment to maintainsynchronization. The accuracy of this synchronization (timing) isdependent upon several factors including, for example, how often and howlong each radio transmits along with other factors.

The purpose of the impulse radio positioning network is to enable thetracking of robots M1 and M2. Tracking is accomplished by steppingthrough several well-defined steps. The first step is for the referenceimpulse radio units R1-R4 to synchronize together and begin passinginformation. Then, when a robot M1 or M2 enters the network area, itbegins receiving the time-of-arrival (TOA) pulses from the referenceradio network. These TOA pulses are converted to ranges, then the rangesare used to determine the XYZ position of the robot M1 or M2 in localcoordinates using a least squares-based estimator. If the situationwarrants and the conversion possible, the local coordinates can beconverted to any one of the worldwide coordinates such as Earth CenteredInertial. (ECI), Earth Centered Earth Fixed (ECEF), or J2000 (inertialcoordinates fixed to year 2000).

Unsynchronized Receiver Tracking Architecture

Referring to FIG. 19, there is illustrated a block diagram of an impulseradio positioning network 1900 utilizing an unsynchronized receivertracking architecture. This architecture is different from thesynchronized receiver tracking architecture in that in this design thereference impulse radio units R1-R4 are not time-synchronized. Similarto the synchronized receiver tracking architecture, robots M1 and M2determine their positions but cannot broadcast them to anyone since theyare receive-only radios. The network is designed to be scalable,allowing from very few robots M1 and M2 and reference impulse radiounits R1-R4 to a very large number.

This particular example of the unsynchronized receiver trackingarchitecture shows a network 1900 of four reference impulse radio unitsR1-R4 and two robots M1 and M2. The arrows between the radios representtwo-way and one-way data and/or information links. Notice that therobots M1 and M2 only receive transmissions from other radios, and donot transmit.

Each reference impulse radio unit R1-R4 is an impulse radio two-waytransceiver, each robot M1 and M2 is a receive-only impulse radio.Precise, unsynchronized pulses are transmitted by the reference networkand received by the other reference impulse radio units R1-R4 and therobots M1 and M2. The robots M1 and M2 take these times-of-arrival (TOA)pulses, convert them to ranges, and then determine their XYZ positions.Since the robots M1 and M2 do not transmit, only they themselves knowtheir XYZ positions.

The reference impulse radio units R1-R4 used in this architecture areimpulse radio two-way transceivers, the robots M1 and M2 arereceive-only radios. The firmware for the radios varies slightly basedon the functions each radio must perform. For this design, the referencemaster impulse radio unit R1 may be used to provide some synchronizationinformation to the robots M1 and M2. The robots M1 and M2 know the XYZposition for each reference impulse radio unit R1-R4 and as such theymay do all of the synchronization internally.

The data-rates between each radio link is a function of severalvariables including the number of pulses integrated to get a single bit,the number of bits per data parameter, the length of any headersrequired in the messages, the range bin size, and the number of impulseradios in the network.

For this architecture, the reference impulse radio units R1-R4 transmitin a free-running (unsynchronized) manner. The oscillators used on theimpulse radio boards often drift slowly in time, thus requiringmonitoring and adjustment of synchronization by the reference masterimpulse radio unit R1 or the robots M1 and M2 (whomever is doing thesynchronization). The accuracy of this synchronization (timing) isdependent upon several factors including, for example, how often and howlong each radio transmits.

The purpose of the impulse radio positioning network is to enable thetracking robots M1 and M2. Tracking is accomplished by stepping throughseveral steps. The first step is for the reference impulse radio unitsR1-R4 to begin transmitting pulses in a free-running (random) manner.Then, when a robot M1 or M2 enters the network area, it begins receivingthe time-of-arrival (TOA) pulses from the reference radio network. TheseTOA pulses are converted to ranges, then the ranges are used todetermine the XYZ position of the robot M1 or M2 in local coordinatesusing a least squares-based estimator. If the situation warrants and theconversion possible, the local coordinates can be converted to any oneof the worldwide coordinates such as Earth Centered Inertial (ECI),Earth Centered Earth Fixed (ECEF), or J2000 (inertial coordinates fixedto year 2000).

Mixed Mode Tracking Architecture

For ease of reference, in FIGS. 20-25 the below legend applies.

Symbols and Definitions

Receiver Radio (receive only) X Transmitter Radio (transmit only)

Transceiver Radio (receive and transmit) R_(i) Reference Radio (fixedlocation) M_(i) Mobile Radio (radio being tracked)

Duplex Radio Link

Simplex Radio Link TOA, DTOA Time of Arrival, Differenced TOA

Referring to FIG. 20, there is illustrated a diagram of an impulse radiopositioning network 2000 utilizing a mixed mode reference radio trackingarchitecture. This architecture defines a network of reference impulseradio units R1-R6 comprised of any combination of transceivers (R₁, R₂,R₄, R₅), transmitters (R₃), and receivers (R₆). Mobile nodes (noneshown) entering this mixed-mode reference network use whatever referenceradios are appropriate to determine their positions.

Referring to FIG. 21, there is a diagram of an impulse radio positioningnetwork 2100 utilizing a mixed mode mobile apparatus trackingarchitecture. Herein, the robots R1-R3 are mixed mode and referenceimpulse radio units R1-R4 are likely time-synched. In this illustrativeexample, the robot M1 is a transceiver, robot M2 is a transmitter, androbot M3 is a receiver. The reference impulse radio units R1-R4 caninteract with different types of robots R1-R3 to help in thedetermination of the positions of the mobile apparatuses.

Antennae Architectures

Referring to FIG. 22, there is illustrated a diagram of a steerable nullantennae architecture capable of being used in an impulse radiopositioning network. The aforementioned impulse radio positioningnetworks can implement and use steerable null antennae to help improvethe impulse radio distance calculations. For instance, all of thereference impulse radio units R1-R4 or some of them can utilizesteerable null antenna designs to direct the impulse propagation; withone important advantage being the possibility of using fewer referenceimpulse radio units or improving range and power requirements. The robotM1 can also incorporate and use a steerable null antenna.

Referring to FIG. 23, there is illustrated a diagram of a specializeddifference antennae architecture capable of being used in an impulseradio positioning network. The reference impulse radio units R1-R4 ofthis architecture may use a difference antenna analogous to the phasedifference antenna used in GPS carrier phase surveying. The referenceimpulse radio units R1-R4 should be time synched and the robot M1 shouldbe able to transmit and receive.

Referring to FIG. 24, there is illustrated a diagram of a specializeddirectional antennae architecture capable of being used in an impulseradio positioning network. As with the steerable null antennae design,the implementation of this architecture is often driven by designrequirements. The reference impulse radio units R1-R4 and the mobileapparatus A1 can incorporate a directional antennae. In addition, thereference impulse radio units R1-R4 are likely time-synched.

Referring to FIG. 25, there is illustrated a diagram of an amplitudesensing architecture capable of being used in an impulse radiopositioning network. Herein, the reference impulse radio units R1-R4 arelikely time-synched. Instead of the robot M1 and reference impulse radiounits R1-R2 measuring range using TOA methods (round-trip pulseintervals), signal amplitude is used to determine range. Severalimplementations can be used such as measuring the “absolute” amplitudeand using a pre-defined look up table that relates range to “amplitude”amplitude, or “relative” amplitude where pulse amplitudes from separateradios are differenced. Again, it should be noted that in this, as allarchitectures, the number of radios is for illustrative purposes onlyand more than one mobile impulse radio can be implemented in the presentarchitecture.

From the foregoing, it can be readily appreciated by those skilled inthe art that the present invention provides a system, a robot and amethod that can use the communication capabilities of impulse radiotechnology to help a control station better control the actions of therobot. The robot can take many different forms and can have atelepresence capability and/or a teleoperation capability.

While particular embodiments of the present invention have beendescribed, it should be understood, however, that the invention is notlimited thereto, since modifications may be made by those skilled in theart, particulary in light of the foregoing. Therefore, it iscontemplated by the appended claims to cover any such modifications orapplications that incorporate those features or those improvements whichembody the spirit and scope of the present invention.

Search and Rescue Operations

One such alternate application contemplated is the use of the robot 902to perform a wide-variety of search and rescue operations. For instance,the robot 902 can be sent in to search for survivors in a building thathas been demolished by some disaster such as an earth quake, explosion,mud slide or the like. In particular, a person can use the centralstation 904 to effectively communicate with and control the actions ofthe robot 902 that is moving around within the demolished building. Incontrast, a conventional central station would have difficultycommunicating with and controlling the actions of a traditional robotdue to the aforementioned “multipath” and “dead zones” problemsassociated with traditional radio communications. In fact, the robot 902can be equipped with a video camera which enables the robot 902 to sendpictures using impulse radio signals to the central station 904. And,the robot 902 can also be equipped with an impulse radio unit that has aradar capability which can detect people located beneath a floor, roofand other debris. Another search and rescue application contemplated isthe use of a robot 902 by law enforcement personnel in a hostagesituation and similiar situations.

Hazardous Locations

Another such alternate application contemplated is the use of the robot902 to perform a wide-variety of operations in a hazardous or dangerousarea. For instance, the robot 902 can be sent in to monitor theenvironment and possibly perform specific tasks in a hazardous locationsuch as a chemical plant or a tank/pipe. In particular, a person can usethe central station 904 to effectively communicate with and control theactions of the robot 902 that is moving around within a hazardouslocation such as a chemical plant or a tank/pipe. In fact, the range ofthe robot 902 located within a pipe can be determined by using one ormore impulse radio units located at one or both ends of the pipe.Another hazardous application contemplated is the use of a robot 902 inspace where the high bandwidth feature of the impulse radio signalsgives the robot 902 a major advantage over traditional robots.

Land Mines

Yet another such alternate application contemplated is the use of therobot 902 to help place land mines. For instance, a group of robots maybe attached to land mines and form an ad hoc network such that ifsomeone removes some of the land mines to make a pathway then the robotscan become aware of which area has been cleared and then jump into thecleared area. These self-healing land mines (robots) don't require theuse of a central station 904 and can use the GPS to help keep track ofwhere they are located with respect to one another.

On the other hand, the robot(s) 902 can be used to help detect landmines so they can be removed or deactivated. For instance, the robot 902including an impulse radio unit that has a radar capability can travelthrough a land mine field and detect the locations of land mines. Therobot 902 can even map the location of the land mines such that they canbe removed or deactivated. To help map the location of the detected landmines, another robot 902 including an impulse radio unit can be used tomonitor the range and/or position of the moving robot 902 that isdetecting the land mines.

Surveillance

Still yet another alternate application contemplated is the use of therobot 902 to perform a wide-variety of surveillance operations. Forinstance, a group of robots 902 in the shape of micro air vehicles canform an ad hoc network that can operate in concert with one another toobtain information such as the presence of chemical weapons, troopsand/or to generate a picture of the ground, a building or amanufacturing center. In other words, the micro air vehicles (robot 902)can be used to obtain a wide variety of information without beingdetected by the people or the things being monitored. In addition, therobot 902 can take the form of a micro unmanned ground vehicle insteadof a micro air vehicle.

Domestic Applications

Still yet another alternate application contemplated is the use of therobot 902 to perform a wide-variety of domestic tasks. For instance, aperson can use the central station 904 to effectively communicate withand control the actions of the robot 902 in the form of a lawn mower orvacuum sweeper. Alternatively, the robot 902 having the form of a lawnmower or vacuum sweeper can be programmed to operate itself and mow alawn or vacuum inside a building by knowing its position through itsinteraction with the reference impulse radio units 1002 and the centralstation 904.

1-20. (canceled)
 21. A method for identifying and locating a physicalasset, said method comprising the steps of: associating a first ultrawideband radio with said physical asset; associating a second ultrawideband radio with a robot; obtaining, at said robot, information thatidentifies said physical asset based upon the interaction of said firstultra wideband radio and said second ultra wideband radio; and locatinga position of said physical asset based upon the interaction of saidfirst ultra wideband radio and at least two of a plurality of referenceultra wideband radios.
 22. The method of claim 21, wherein said physicalasset is at least one of a commercial asset, a military asset, a work ofart, a computer, and a cash drawer.
 23. The method of claim 21, whereinsaid physical asset is located inside a building.
 24. The method ofclaim 21, further comprising the step of: interfacing said robot with acontrol station.
 25. The method of claim 24, wherein said controlstation is used to control said robot.
 26. The method of claim 24,further comprising the steps of: determining a position of said robotbased upon the interaction of said second ultra wideband radio and atleast two of a plurality of reference ultra wideband radios; andcontrolling the actions of said robot based upon said position of saidrobot.
 27. The method of claim 24, further comprising the step of:conveying said information that identifies said physical asset from saidrobot to said control station, wherein said control station uses saidinformation that identifies said physical asset to monitor said physicalasset.
 28. The method of claim 24, wherein said control station islocated remotely to said robot.
 29. The method of claim 24, wherein saidsecond ultra wideband radio communicates with a third ultra widebandradio associated with said control station.
 30. The method of claim 21,wherein the second ultra wideband radio has radar capabilities which areused to detect a person in the vicinity of the robot.
 31. The method ofclaim 24, further comprising the step of: interfacing said robot withone or more sensors, wherein said control station uses informationobtained from said one or more sensors to monitor said physical asset.32. The method of claim 21, wherein said first ultra wideband radioperiodically wakes-up from a sleep mode to transmit at predeterminedintervals the information that identifies the physical asset.
 33. Themethod of claim 32, wherein said first ultra wideband radio listens fora transmission from said second ultra wideband radio for a period oftime following the transmission of the information that identifies thephysical asset.
 34. The method of claim 33, wherein said transmissionscomprise at least one of a range request and a status request.
 35. Themethod of claim 21, further comprising the step of: determining a rangebetween said first ultra wideband radio and said second ultra widebandradio.
 36. A physical asset location system, comprising: a first ultrawideband radio associated with a physical asset; a robot associated witha second ultra wideband radio that interacts with said first ultrawideband radio to determine information that identifies said physicalasset; and a plurality of reference ultra wideband radios, at least twoof which interact with said first ultra wideband radio to enable aposition of said physical asset to be determined.
 37. The physical assetlocation system of claim 36, further comprising: a control stationhaving an interface with said robot.
 38. The physical asset locationsystem of claim 37, wherein said control station is associated with athird ultra wideband radio that interacts with said second ultrawideband radio.
 39. The physical asset location system of claim 36,wherein at least two of said plurality of reference ultra widebandradios interact with said second ultra wideband radio to enable aposition of said robot to be determined, wherein said determinedposition is used to control one or more actions of said robot.
 40. Thephysical asset location system of claim 36, further comprising: at leastone sensor associated with said robot.